Electric switch



Dec. 23, 1952 w. H. V OGELSBERG ELECTRIC SWITCH 3 Sheets-Sheet 2 FiledApril 25, 1950 Dec. 23, 1952 w. H. VOGELSBERG ELEICTRIC SWITCH 3Sheets-Sheet 35 Filed April 25, 1950 the contacts I and II are engaged,a clrcuit is established from the supply line 2, through adjustableblade I2 contacts I0 and II, through heater B to the heating load I andthence to line 2. When the contacts I0 and II are separated, the heatingload is deenergized. A control knob I3 er some other suitable manualadjusting means is provided on the oontrol device 4 for selecting thedesired input to the heating load. The adjustment is efiected by themanipulation of the flexible blade I2 through a screw memher I4.

The operation of this partieular thermostatic clevice can be explainedby follovving a typical cyole of closing and opening of the contacts I0and II. Assume that the contacts I0 and II are separated and that thethermomotive means 4 is cooling. In this oondition, the free end of thethermomotive member 4 moves to the right. Upon engagement of contacts I0and II, current fiowing through the heater leg 6 will cause it to heatrapidly, expand longitudinally and force the free end of thethermomotive member 4 farther I:=o the right. As the leg B continues toheat, the bimetal leg 5 will receive heat therefrom and Will begin toflex and move the contact I0 towarcl the left. This motion will continueuntil the contacts separate, thereby deenergizing the heating load anddiseontinuing the current supply to the leg 6. Immediately uponseparation of the oontacts I0 and II, the leg 6 will quickly cool,contraot and so force the thermomotive member 4 farther to the left.Furthercooling of the thermomotive member 4 Will cause the bimetallicleg 5 to return toward its unflexed position, permit the oontacts I0 andII to be reengagecl and thus start another cycle of operation.

It Will be observed that both the bimetal 5 and heater 6 contribute tothe thermoinotive aotion of the swltch but that the thermomotive effeotof the primary element 5 is always arranged to supersede the effeot ofthe secondary element That is to say, the 1orimary element 5 is the more-active er more efiective in that it always ultimately dominates theaction of the secondary element 6 in effeoting opening and olosing ofthe switch contaots on heatin and cooling respectively. The effect ofthe additional thermomotive aetion offered by the heater 6 is toprovicle a differential between the opening and olosing temperatures ofthe bimetal 5 which in turn efiects a greatly inoreased cycle length.The length of the time cycle is now made up of the undershoot andovershoot of the bimetal plus the increased cycle length due to theaetion of the heater. It

should be noted that i-f the heater were not mechanically connected withthe bimetal, no differential would exist and the entire cycle wouldconsist; of the time necessary for the bimetal to overshoot andundershoot.

The utilization 015 the the1moh1otive aotion offei*ed by the heater isconsidered of maximum importance in the application of this device, andparticularly when this device is to be used in conjunction with thefiashing or the overenergizing of an electric heating unit so that ltcan attain its operating temperature quickly. In my copendingapplication, Serial N0. 81,938, filed March 17, 1949, systems anddevices are shown which utilize a Single thermal Wattage controller tocontrol the length of the overenergization period and also to controlthe input during normal energization by cyclically opening and C1OSillgof the oircuit to the electric heating unit. A wattage oontr0ller soadapted must meet many severe requirements. First, it must possess thosefeaw tures so essential in the application of the device as an ordinarywattage oontroller; it must be reliable, simple to manufacture, etc.,and it must have moderately long cycles. Secondly, to meet therequirement of adaptability to a. flashing system as above mentioned, itmust heat and cool at substantially the same rateas the heating unit itis controlling. Thus lt must be a thermal prototype of the eleetricalload (i. e the heatlng unit) it is controlling. In these fiashingsystems. the heater for the wattage controller has an energization rateproportional to that of the beatin unit. Dlllil'lg the overenergizationinterval. the wattage oontroller acts to time the duration of theoverenergization. When the controller attains a temperature proportionalto the desired operating temperature -of the heating unit, the contactsopen and terminate the flash interval. Thereafter the controller, havinga reduced energization rate proportional to the reduced energizationrate of the heating unit aets to control the wattage input level to saidunit by cyelically opening and closing the circuit thereto. The abilityof the wattage controller to track the heating unit thus permits it toact as a safety device if a refiashis attr'empted, for the temperaturewhich the controller must attain is reduced an amount 'oorresponding tothe temperature of the heating unit at the tlme a reflash is attempted,thereby preventing sueoessive reflashing for extended perlods of timewhich might result in dangerous overheating of the heating unit. 3

A unique problem is presented when it is desired to provide a thermalc-ontroller that will give long cycles as well as have the ability totrack the heating unit, without resorting to snapaotion switohes. T0obtain moderately long. oycles in the past lt was necessary increase thethermal mass of the switch, thereb inore'asing the undershoot andovefShoot of the associated thermal element in a manner well known inthe art. To cause the controller to tra.ck the heating unit, it isnecessary that the thermal capacity and the thermal dissipative capacityof the thermal element of the controller be of the proper magnitudes.These two requirements are not consistent with one another, it beingonly a fortuitous combination of circumstances or severe comprom'isesthat would permit previous arrangements to be used. However, by usingthe present invention wherein the thermomotive action of the heater 6 isused to obtain the long cycle independent of the heat storage capacityof the mass associated With the thermal element, wide latitude ispermitted in designing a controller with the correct prototypecharacteristics.

A physical embodiment of the above described form, adapted to a controldevice of the character disclosed in my oopendin applieation Seria1 N0.157,933 filed April 25, 1950, is shown in Figs. 2 to 9. Only that partcf the device involving the present invention need be described.

In these figures, there is shown a control device comprising a controlbox or oasing I5 onto which is flxed-a cover member I6 by means ofscrews I'I. A control knob I8 serves to control the position of anadjustable bl'ade I0 through a oontrol cam 20 carried by a shaft 2Iwhioh is rotatably supported by cover I6 and the rear of the casing I5in a pil-ot hole 22. The adjustable blade I0, a relatively heavymetallic member. has affixed to its free end a contact 23 whichcooperthe adjustable controiIblagle I9 argWelgled-foblade 32 through anins ula} tin g b1t1qgn 33. mounted thereon to isolatge ohe cor 1 tmlblade electrically and thermally from said compgansator, Near the centerof the a;djustaeblade I9 is'a landed projectiom 34 whichcoactswith thesu 1& face of the control cam2il.

The construction and the arrangement of the masses as shown for thecomponent ;partsof the adjustable blade and mounting l9,25 haveprovenquite satisfactcry in eliminating excessive vibra tion prevalent in-devices that have extremely flexible contact support members. Tl1ecqnstruction is also advantageousbecause 117 permits a very convenientway cf institutirgg the comp epn sating action and in addition the-factory adjustment, which Will be explainedhereinaftern It should bementioned that-the details of the cam are describ-ed at length inthe-aforementioned copending application.; Of :parti cular interest isthecam program -that provi'des a, comtinuous selection of inputs fromsome 10W value to a-ful1 100% input-position. In that applicaticn thecircuit in which the wattage controller is used does not require thatthe contacts 2'31a11d carry the continuous 100% 1oad;an auxiliarypathbeing provideid therefojrv Thepresentinvention is capa'ble ofapplication tothistype of circuit o1 an arrangement whera 1hewontactsare -maintained clo-sed by the cam throW to' give" the* 100% input. Thecam =is further provid'ed With 2 recessed. offpositionatfi0a; insufing agene1ouselectrical clearance at this partilcular switch conditioning:

The thermomotive means 25 (see Fi gs. 6 to 8) consists of asubstantially"straight' control bimetal 35 and aheater element 35 cf;hightemperature material, such as a, nickel chrome a11oy, having anarrow sec tion '31.Whi0hf8Xtlld3 a greater portion of its length;Thebimetal 35, the heater element- 35, and the electrical c'ontact 24..are Welded together using a; stee1 .button 391 th Cyclic heating anticoolling pf the; thermonio-- tiye n1eans 25.

35 than with the bimetal 35, anc'f that;ah air a trminal meinbe r 50,Ehe loweiy part of the oigher. It will be noted that 2zr; i- 1113501Strip 52 is interpcised"betvveenfthejheald" of thriiretj 2ind formed inthe casing 'to pxqvgrlxtfthethiarmpe is maintained subStantiallycoristetht1egardles's of changesin ambitaixt*temperatures* tcr=which thedevice is eXposed.:-The bilrnalrcompensator is disposed Witt 1 its highexpangionsidenward; i.e. toward the leit; as -viewed ir 1 Figs.; *2 a11d 6:

7 surface of control cam 20 and so rotates the free end of the controlblade toward the 1eft.

The compensator 32 is prevented from movement other than that to achievethe compensating action. A recess 51 provided in the casing, aprojeotion 58 adjacent the fixed pivot or fulcrum 54 and a pin 54bthrough a hole 32a in the compensator 32 locate oho compensator in the1ower portion of the casing. The adjusting screw 55 permits oontrol ofthe controller calibration by varying the position of the lower end. ofthe control blade I9. Thus if the inputs to the heating unit are inexcess of what they should be for a particular setting of the controlknob I8, it wou1d be necessary decrease the temperature or deflection abwhioh the contro1 contacts 23 and 24 separate. This wou1d means that theInitial position of contact- 23 would have to be disposed farther oo theright, as viewed in Figs. 2 and 6, which can be achieved by backing oflthe adjusting screw 55 thus allowing the compensator to pivot clockwise(Fig. 5) about fulcrum 54, displacing the 1ower end of the control bladeI9 toward the 1eft.

The electrical and thermal operation of this device is similar to thatshown diagrammatically in Fig. 1. The :urrent path is through thetermina1 member 28, through the rivet; 21, through ehe mounting spring26, the control blade I9, contact 23 and contact 24, through the heater36, rivet 40 and out through the terminal member 50. The meohanicaloperation can be followed in Fig. 2. Rotation of the control knob 18 to0ne of the on positions will cause translation of the adjustable Madetoward the left with consequent estab- 1ishment of the circuit throughcontacts 23 and 24. The adjustable b1ade is manipulated through thelanced portion 34 and engages at its upper end the contact 24 of thethermomotive means 25, whi1e at its lower end it engages the insu1atingbutton 33 of the compensator. During the heating cyole of thethermomotive means 25 the adjustable blade through contact 23 followsthe motion of oontact 24 until separation is efiected. Under thiscondition and throughout; the ofi portion of the cyc1e the blade takesup an equilibrium position as determined by the cam 20, the compensator32 and the positioning efiect 015 the mounting spring 26.

Of importance in the design of the thermomotive means 25 is the ofiset59 provided on ehe heater 36. It has been found that this featureconstitutes (a) a convenient means for preventing overstress in theheater during its expansion and contraction; (b) a means to vary theamount of mechanioal infiuence of the heater on the bimetal Which inturn effects the length of ehe time cyc1e; e. g. increasing the offsetwhile still maintaining the spacing between tne heater and bimetal thesame will decrease the length of the cyc1e; (c) a means of preventingoverstressing of the top fibres cf the g1ass cord wrapping by reducingthe lateral foroe during compression of. the heater.

In one particular structural embodiment of this invention, thebimetallic member 35 was made from a material having a high expansionside of 72% manganese, 18% copper, and 10% nickel, whi1e the lowexpanding side was =of Invar. A third layer of nicke1 was providedbetween the high and low expansion sides to give a desired lowelectrical resistance to the entire bimetal. The length from the center1ine of the mounting rivet 43 to the top 013 the bimetal wasapproximately 8 2%", ehe width along the major portion of the 1ength at.218" while the thickness was .030".

The heaoer 36 was maae from a material composed of nickel and 20%chromium which was annealed after being formed into the shape shown inFig. 6. The width a1ong the greater part of its 1ength was .096" with athickness of .005", the effective length of this necked-down portionmeasuring 1%,". a as shown in Fig. 6 Was %4. The thickness of theinsulating medium was .034" for the as-- bestos strip 4l and .001" forthe mica strip 42.. The asbestos was selected from a 1ong fibre stock of.042" in thickness which was subsequently compressed to theaforementioned thickness.

The particular 1oad used with this wattase coutroller was such as topass approximately 5 amperes through the heater.

The compensator bimetal 32 was selected from a material having the highexpansion side o1 72% manganese, 18% copper and 10% nickel, whi1e thelow expanding side was of Invar. Its Width at the widest point was .340having a thickness of .022" with an effective length of approximately 1with the fulcrum at the widest point looated about 1 from the center ofthe button 33.

A modified form of the invention is shown in Figs. 10 to 12 to comp1isea thermomotive member 60 and an adjustable member 61 having cooperatingcontacts 62 and 63 mounted thereon. The thermomotive member of thisembodiment comprises two parallel bimetallic members 64 and 65 hold inspaced relation and placed with their low expansion sides facing eachother. An insulating and separating member 66 is disposed between thesebimetallic members and a g1ass cord wrapping 67 is provided around thesemombers to maintai1mthe mechanical and thermal rel-ation so one another.Electrical connection is ensured between the tops of bimetals 64 and 65by means of the flexible conductor 68 hold under the contaot 52 onbimetal 65 and through a rivet 69 to bimetal 64. Aside from themodifications shown the device is similar to the previously describedform.

The operation of the thermomotive member 60 is substantially the same asthe above-described device, for as the contacts first make, the bimetal64 which also acts as the heater forces the free end of the primarybimetal 65 farther to the right. The thermomotive action 01 the bimetal64, however, results from the flexing due to its regular bimetallioaction rather than from a change in its overall length. As heatingcoutinues, the bimetal 65 will flex to -tloe leih, over coming the forceexerted by the heater bimetal 64, and eventually efiect Separation ofehe nontacts 62 and 63. Upon first separacion of the contacts the heaterbimetal will cool rapidly, exerting a force toward the leih through theglass cord wrapping thereby substantially augmenting the oontactseparation. Hera as in the previous embodiment the thermomotive efieotof the secondary or heater element is arranged to be superseded by thatof the primary olement.

In a physical embodimen, the material for bimetal member 65 was similarthat used for bimetallic member 35 having the same general dimensions,while the secondary bimetallic member 64 was of .020" thick material ofthe same composition as the compensator bimetal 32. The narrowed sectionof the secondary member 64 had an approximate efiective 1ength of 1fg"and a width of 1%"- The insulating medium 56 was The offset dimensionbetween said members, the less active member having an offset to preventoverstressing thereof ancl t control the diiferential between thetemperatures of the more active member at opening and. closing of saidelectrical connections, the initial heating of said less active memberca1ising a rapid thermomotive action in opposition to the thermomotiveaction of said more active member on heating, and the initial cooling013 said less active member causing rapid movement in opposition to themovement of said more active member an cooling.

7. In an input control switch, thermomotive means having a free end anda fixed end, said means comprising two thermomotive members ofthermomotively dissimilar materials disposed in substantially parallelspaced relation, with rigid mechanical connections between said membersat two points, thermal insulating means disposed between said members,electrical connections including contacts cyclically operable by thefree end of said thermomotive means for supplying energy 130 the lessactive of the two members to rapidly heat the same during each cycle,the more active member receiving heat from the less active member, andmeans for holding said members and the associated therma1 insulatingmeans in close constant association with one another, ehe initialheating of said less active member causing a rapid thermomotive actionin opposition to the thermomotive action of said more active member onheating, and the initial cooling of said less active member causingrapid movement in opposition t;o the movement; of said more activemember on cooling.

8. In an input contro1 switch, a thermomotive means having a free endand a fixed end, said means comprising two thermomotive members ofthermomotively dissimilar materials disposed in substantially parallelspaced relation, with rigid mechanical connections between saiol membersat two points, thermal insulating means disposed between saicl members,electrical comnections including contacts cyclically operable by thefree end of said thermomotive means for supplying energy 120 the lessactive of the two members to rapiclly heat the same during each cycle,the more active member receiving heat from the less active member, thelatter member being relatively thin so as to have W mass and highelectrical resistivity, and means associated with the latter member 130prevent buckling thereof, the initial heating of said less active membercausing a rapid thermomotive action in opposition to the thermomotiveaction of said more active member on heating, and the initial cooling ofsaid less active member causing rapid movement in opposition to themovement of said more active member on cooling.

9. In an input control switch, thermomotive means having a free end anda fixed end, said means comprising two thermomotive members ofthermomotively dissimilar material dlsposed in substantially parallelspaced relation with rigid mechanical connections between said membersab two points, thermal insulating means disposed between said members,electrlcal connections including contacts cyclically operable by thefree end of said thermomotive means for supplying energy to the lessactive of Ehe two members 1:0 rapidly heat the same during each cycle,the more active member receiving heat from the less active member, meansfor holding said members and the associated thermal insulating means inmeans to facilitate relative motion between the less active member andsaid thermal insulating means, the initial heating of said less activemember causlng a rapid thermomotive action in opposition 110 thethermomotive action of said more active membefon heating, and theinitial cooling of said less active member causing rapid movement inopposition to the movement 0f said more active member on cooling.

10. In an input control switch, thermomotive means comprising a pair ofoppositely-acting bimetallic heat-expansibe members having differentdegrees cf heat expansivity, said members being disposed insubstantially parallel spaced relation and being rigidly connectedtogether ab one end, means securing said members together alongsubstantially their entire length while permitting relative slidingtherebetween, currentcontrolling contacts controlled by saidthermomotive means and adapted when closed to effect; current heating ofthe member having the lower heai: expansiyity. the member having thehiger heat expansivity receiving heat from the member having the lowerheat expansivity, and said coutacts being con trolled by conjolnt actionof said members.

11. In an input control switch, thermomotive means comprlsing a palr ofthermomotively dissimilar members, sa1d members being disposed insubstantially parallel spaced relation, with mechanical connectiongbetween said members adjacent the fixed ends am). at least at one pointalong the lengths of said members, a contact carried by saidthermomotive means and electrically connected to the member having thelower heat expansivity, a manually-adjustable contact arrangedcooperatively with said first contact, said contacts when closedefiecting currenc heating of the member having the lower heat expansiVity, the member having the higher heat expansivity receiving heatfrom the member having the lower heat expansivity, and said (3011- tactsbeing controlled by conjoint action of said members, the lnitial heatingo1 said less active member causing a rapid thermomotive action inopposition to the thermomotive action of said more actiVe member onheating, and the initial cooling cf said less active member causingrapid movement in opposition to the movement of said more active memberon cooling.

12. In an input control switch, thermomotive means comprising a pair ofthermomotively dissimilar members, said members being disposed insubstantially parallel spaced relation, witl1 ms chanical connectionsbetween said members ad jacent the fixed ends and at least ab one pointalong the lengths of said members, a contac carried by said thermomotivemeans and electrically connected to the member having the lower heatexpansivity, a manually-adjustable contact arranged cooperatively withsaid first contact means including a compensator element for positioningSaid second contact according to ambient temperatyre, said contacts whenclosed eflecting current liea'ting of the member having the lower heatexpaiisivity. the member having tne higher heat expahsivity receivingheat from ehe member having the lower heat expansivity, and saidcontacts being controlled by conjoint; action of said members, theinitial heating of said less active member causing a rapid thermomotiveaction in opposition to the thermomotive action of said more activemember on heating, and the c1ose constant association with one anqther,and initial cppling of said less act1ve member sausing rapid movement inopposition to the movement f said more active member on cooling.

13. An input control switch according to claim 12, including means f01efiectin initial adjustment of said compensator elemenu.

14. An input control switch ac-eording t-o claim 12, including a springsupporu f01 said second contact an adjusting arm connected 120 saidsupport and movable loy said compensaoor element, and amanually-adjustable eam engaging said arm.

15. An input svvitch according 50 claim 14- wherein said compensator isdisposed ab a 1ight angle to the adjusting arm.

16. An input control1er for supplying a predetermined average wattageinput 170 a remotely connected heating load, comprising: ci1cuitControlling, connections including contacts adapted to be cyclicallyclosed and opened, the relative lengths 01 the c1ose and open intervalsdeterd mining the average wattage input to said load; means forinitially efiecting Closure of said comtacts to starb an input controlfunction; thermomotive means operative 120 cyclically open and closesaid contacts, said thermomotive means comprising a primarythermal-responsive memher having a relatively high thermomotivecharacteristic and a re1atively high eifective thermal mass operableupon heating to effect opening of said contacts and operable uponcooling 110 effect closing of said. contacos, and an oppositely-actingsecondary thermal-responsive member haVing a relatively lower efiectivethermomotive characteristic and a relatively lower efiective thermalmass mechanicaliy coupled to said primary memleer for conjointthermomotive action of the two members and for transfer of heattherebetween; said circuit controlling connections being ar- 1anged toeffect heating of said secondary memher when the contacts are closed,thereby to effeet an initially rapid thermomotive action of saidsecondary member tending 120 maintaiu said contaccs closed and lengthenthe on cye1e, and subsequent greater thermomotive action 01 said primarymember, in response to heat transferred thereto from said secondarymember, effective to open said contacts, whereupon the heating ef saidsecondary member is interrupted and. the latter cools rapidly efiectingaugmented opening cf said connectiong and lengthening of the 011 cycle.

17. An input controller according 110 claim 16, wherein saidthermomotive means comprises a bimetal primary member naving a movableportion, and a rapidly expansible and contractlble currenc-concluctingsecondary membey having one end fixed said movab1e pertien, saidsecondary member serving, by its rapid expansion and contraction, toefiect the desirecl secondary thermomotive action.

18. In an input control switch, a thermomotive means having a free endand a fixed end, said meang comprising two thermomosively dissimilarmembers disposed in substantially parallel spaced relation, said member5being rigidly connected together ab two points, therrnal insulatingmeans disposed between said members, electrical C011- nections includingcontacts cyclically operable by the free end of said thermomotive meansfor supplying energy to the less active of the two members to rapidlyheat the same during each cycle, the more active member receiving heatfrom the less active member, the latter member being relatively thin soas have 10W mass ancl high electrical resistivity and having arectangular cross-sectien With the broader surface thereof disposedparallel 120 said more active member, and means securing said lessactive member to said. more active member along their entire lengthbetween said two points to prevent buckling of said less active memberand to maintain a c1ose constant association between said members whilepermitting relative sliding motion between said members, the initialheating of said less active member causing a rapid thermomotive acaionin opposition the thermomotive action of said more active member onheating, and the initia1 cooling of said less active member causingrapid movement in opposition to the movement of said more active memberon cooling, the thermomotive action of said more active member 011heating and cooling ultimately dominating the thermomotive action ofsaid lass -active member on heating and cooling respectively.

WALTER I-I. VOGELSBERG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNI'IED STATES PATENTS Number Name Date 908,679 Kelley Jan. 5, 19091684,709 Lowenstein Sept. 18, 1928 1,924647 McGregor Aug. 29, 1933

